Gray Smoke?

got a 1066 recent overhauled the engine and when i pull it and leave the line the smoke is Gray then it clears up and smokes black on the other end when it starts pulling the engine down what could be causing this? Bad injectors? or not enough fuel?

I would do a pressure test of the cooling system just to remove any possibility of a leak.

My guess would be timing.

does it run good at the end of the track were it matters? it might just be the nature of the beast,

My guess is that if you are getting a little water down in the cylinders or atleast a couple. Same as the water injection on our pulling tractors. At lower rpms and lack of heat it will make the exhaust gray and then clear out but that is a timed thing in our tractors. If you go to a tractor pull with super farms or prostocks you will see this also as they bring the rpms up in them. In their case it should go white to gray to flame(also known as the cone) to black. the white in their case is just unused fuel. Do a pressure check on the cooling system and make sure that everything is seated exspecially if you have been inside of it. Also if you have been inside of it was it broke in correctly? May be a head gasket didnt seat right and is losing alittle water down in the cylinders. I suppose you could also have a fouling injector and it is not putting out the correct amount of fuel at the lower rpms and leaning out a cylinder changing the smoke color. I would check for water in the cylinders and go from there. I would most defently try to figure out what it is because it could become a larger problem later on. If it is water it will sooner or later push wherever it is leaking all the way out of it. If it is fuel it could burn piston or wreck the valves and hurt the motor badly. If you got anymore questions let us know. Goodluck Jay